1. Field of the Invention
The present invention relates to an exposing apparatus which projects an image of a predetermined pattern by a projection optical system, and an exposing method using this exposing apparatus. In a lithography step for producing various devices such as a semiconductor device and a liquid crystal display, the invention is suitably used for transferring a mask pattern onto a substrate.
2. Description of Related Art
In a lithography step which is one of producing steps of a semiconductor device, an exposing apparatus such as a full field exposing type projection exposing apparatus like a stepper, and a scanning exposing type projection exposing apparatus like a scanning stepper is used for exposing and transferring a pattern formed on a reticle (or photomask) as a mask onto a wafer (such as a glass plate) as a substrate on which a photoresist is applied.
In such exposing apparatuses, rigidity of a stage which positions or moves a reticle and a wafer, rigidity of a support mechanism of the stage, and rigidity of a mechanism portion of a support mechanism of a projection optical system exert a great influence on performance of apparatus such as vibration isolating performance and exposure precision (superposing precision), the weight of the mechanism portion and producing costs of the exposing apparatus. Generally, an exposing apparatus having a mechanism portion of high rigidity has high apparatus performance, but there is a tendency to increase the weight of the mechanism portion and to increase the producing cost. Hence, to reduce the weight of the entire mechanism portion while maintaining high rigidity of necessary portions of the apparatus, there is proposed an exposing apparatus which independently supports bases such as a reticle stage and a wafer stage by a parallel link mechanism having a plurality of rods which can extend and contract (e.g., see an International Patent Application Publication Laid-open No. 01/022480).
Lately, to enhance a resolution, there is also developed an immersion type exposing apparatus which supplies liquid between a projection optical system and a wafer (see an International Patent Application Publication Laid-open No. 99/49504).
According to the conventional method using the parallel link mechanism having the plurality of rods which can extend and contract, it is possible to reduce the weight of the mechanism portion and to enhance the control precision of a moving portion of a stage, but there is a fear that the structure of the mechanism portion becomes complicated, and the positioning of the stage and control at the time of acceleration and deceleration become also complicated.
In the exposing apparatus, a sensor for measuring a positional relationship between the projection optical system and the wafer stage is used. In the conventional technique, the sensor is integrally supported together with the projection optical system. Even if the projection optical system and the sensor are integrally supported using a support member having high rigidity, however, there is a fear that the positional relationship between the projection optical system and the sensor is varied beyond the permissible range due to influence of vibration from a floor or irradiation heat of illumination light for exposure. Further, according to the structure in which the projection optical system and the sensor are integrally supported, there is a problem that the adjusting time required until the positional relationship therebetween is set to a predetermined target positional relationship is increased when the exposing apparatus is assembled and adjusted, and time required for maintenance of the projection optical system and the sensor is also increased.
In the conventional immersion type exposing apparatus, since a portion of an device which supplies liquid between the projection optical system and a wafer is integrally supported together with the projection optical system, there is a fear that vibration generated in the liquid supply device is transmitted to the projection optical system, and exposure precision is deteriorated.